Prediction of growth response in prepubertal children treated with growth hormone for idiopathic growth hormone deficiency.

Several multiple regression models have been developed to predict the first-year growth response to human growth hormone (hGH) in children with growth hormone deficiency (GHD). It was the aim of this study to analyse the significance of various growth parameters for a height prediction model. Data from 148 prepubertal children with idiopathic GHD were evaluated. The prediction model was developed by means of univariate and stepwise linear regression analysis and an "all possible" regression approach using Mallow's C(p) statistics. Six out of eight selected variables had a significant influence on the first-year growth rate. The most important parameter was the difference between target height SDS and height SDS at the start of therapy (THSDS-HSDSCO), accounting for 23.95% and 25.74% of the variability. No other single variable or combination of variables was more informative than the variable THSDS-HSDSCO alone. From these data, growth velocity for the first year of hGH treatment was estimated as 1.106 (THSDS-HSDSCO) + 6.8 cm/y +/- 2.2 cm (SE), allowing a prediction for different intervals between THSDS and HSDSCO. This equation was validated in a small group of 18 GHD patients demonstrating a predicted vs. observed first-year growth rate of 9.4 +/- 1.1 vs. 9.5 +/- 2.6 cm/y. We conclude that the difference between THSDS and height SDS at the start of therapy is an important predictor of the first-year growth response in children treated with hGH for idiopathic GHD. Unlike in previous studies, additional parameters did not increase predictability.